Police in Colombia have arrested a Cuban man suspected of plotting to kill American diplomats in the name of the Islamic State.

Police in Spain said Thursday they had been monitoring the online activities of the suspect, Raul Gutierrez, and that over a period of several weeks he showed signs of gradual indoctrination in radical Islam. In late February he allegedly said he had obtained an arsenal of explosives that he planned to detonate at a popular dining area in Bogota frequented by U.S. diplomats.

He was arrested Monday in the western city of Pereiera as a result of the operation between Spanish authorities, the FBI and Colombian police.

Gutierrez pleaded not guilty in his first court appearance Wednesday.

The U.S. Embassy in Colombia did not immediately comment.